Isolation and characterization of a lectin from the cephalochordate Branchiostoma lanceolatum (Pallas)

A new lectin from the sea worm Serpula vermicularis: isolation, characterization and anti-HIV activity

A GlcNAc-specific lectin was isolated from the sea worm Serpula vermicularis (SVL) (Annelida) and purified by ion-exchange, affinity and gel permeation chromatography. SVL was a homotetrameric protein with native molecular mass of about 50 kDa, and consisted of identical subunits of 12.7 kDa. The carbohydrate content of 1.9% suggested that the lectin was a glycoprotein, and mainly composed by aspartic and glutamic acids, glycine, valine and serine; with relatively lower content of basic amino acids and cysteine. The first 15 residues of the N-terminal region were determined as ADTPCQMLGSRYGWR. It was stable at pH 6-9 and at temperatures up to 40 degrees C. SVL was Ca(2+)-independent lectin that agglutinated native and trypsinized human erythrocytes. Hapten inhibition studies indicated that SVL showed binding specificity only for N-acetyl-d-glucosamine and its derivatives among the monosaccharides tested and required the presence of hydroxyl group at the C-3 of GlcNAc. The presence of hydrophobic p-nitrophenyl aglycone improved inhibitory potency of N-acetyl-d-glucosamine. Ovomucoid and ovalbumin were found to be inhibitors among the glycoproteins used for inhibition assay. The anti-HIV-1 (human immunodeficiency virus) activity of SVL in vitro was determined: SVL inhibited the production of viral p24 antigen and cytopathic effect induced by HIV-1. The EC(50) values were 0.23 and 0.15 microg x mL(-1) respectively.

A beta-galactose-specific lectin isolated from the marine worm Chaetopterus variopedatus possesses anti-HIV-1 activity

A 30 kDa beta-galactose-specific lectin named CVL was isolated from the polychaete marine worm Chaetopterus variopedatus (Annelida) and its anti-HIV-1 activity in vitro was determined. Results showed that CVL inhibited cytopathic effect induced by HIV-1 and the production of viral p24 antigen. The EC(50) values were 0.0043 and 0.057 microM, respectively. Time-of-addition analysis of anti-HIV-1 activity indicated its action was at the early stage of virus replication. CVL could blocked the cell-to-cell fusion process of HIV infected and uninfected cells with an EC(50) of 0.073 microM. The inhibition of HIV-1 entry into host cells was demonstrated by using fluorescence-based real-time quantify PCR. At CVL concentration of 0.33 microM and 0.07 microM, 86% and 21% virus attachment were blocked, respectively. The anti-HIV-1 action of CVL might relate to blockade of HIV-1 entry into cells.

Isolation and characterization of an acetyl group-recognizing agglutinin from the serum of the Indian white shrimp Fenneropenaeus indicus

A natural agglutinin from the serum of the Indian white shrimp Fenneropenaeus (Penaeus) indicus was purified to electrophoretic homogeneity by a single-step affinity chromatography on N-acetylglucosamine-Sepharose 6B. The expression of hemagglutinating (HA) activity of F. indicus agglutinin (FIA) was independent of the presence of divalent cations and insensitive to their chelators. FIA gave a single symmetrical peak in its native form with a molecular mass estimate of 200 kDa on gel filtration in HPLC, and SDS-PAGE under reducing conditions revealed that it is a homo-oligomer of a 27-kDa subunit protein. The pattern of reactivity of FIA against anti-FIA rabbit serum in immunodiffusion and immunoelectrophoretic analysis provided additional evidence for its purity and homogeneity. HA-inhibition studies documented exclusive specificity of FIA for acetyl groups in carbohydrates independently of the presence of these groups at the C-2 or C-5 position and its stereochemical arrangement in the axial or equatorial orientation. The unique ability of FIA to recognize acetyl groups was also explicitly demonstrated with sialo- and asialo-glycoproteins. Strikingly, FIA also interacted equally with amino acids and chemicals containing acetyl groups, thereby unambiguously demonstrating the exquisite specificity of FIA for an acetyl group, irrespective of the presence of this group in carbohydrate or noncarbohydrate ligands. The susceptibility of HA activity of FIA to inhibition by lipopolysaccharides from diverse gram-negative bacteria as well as its ability to selectively agglutinate several bacterial species isolated from infected shrimps implicate a potential role of this humoral agglutinin of F. indicus in the host immunodefense reactions against microbial invaders.